code: def test_HandleUnknown_HaveNoUnknownInTrain_ExpectIndicatorInTest(
      self,
  ):
      train = ["A", "B"]
      test = ["A", "B", "C"]
  
      encoder = encoders.OneHotEncoder(
          handle_unknown="indicator", handle_missing="value"
      )
      encoder.fit(train)
      result = encoder.transform(test)
  
      expected = [[1, 0, 0], [0, 1, 0], [0, 0, 1]]
      self.assertEqual(result.to_numpy().tolist(), expected)
  
imports: import pandas
  from unittest import TestCase
  import numpy
  import tests.helpers
  import category_encoders
label_desc: Use image node_id 17 for calling the TestOneHotEncoderTestCase obj's underlying member method code with example usage: obj.test_HandleUnknown_HaveNoUnknownInTrain_ExpectIndicatorInTest() without return types